(a) Field of the Invention
The present invention relates to an optical pick-up device, and in particular, to an optical pickup actuator capable of controlling tilt for recoding information signals on a high density optical disc and reproducing the same therefrom.
(b) Description of the Related Art
Recently, as high density optical media have been developed, various optical pick-up devices have been researched and developed for recording information signals on the optical media and/or reproducing the signals therefrom.
The optical pick-up is a core part of optical recording/reproducing device. Information recorded on an optical disc is converted into optical signals in forms of laser beams generated by a laser diode installed in the optical pick-up. The optical signals are received by a lens of an actuator in the optical pick and then converted into electrical signals by an optical element.
The optical pickup actuator moves an objective lens with a bobbin so as to maintain relative position between the objective lens and the optical disc and write information into or read the same out of the optical disc along tracks defined on the disc.
The optical pick-up actuator moves the objective lens to a required position in accordance with cooperation between and magnets and coils arranged in a magnetic field formed by the magnets. The movable part is designed to be fixedly supported by a supporter (suspension wire) so as to obtain required frequency characteristics, can move in two directions, i.e., a focusing direction and a tracking direction, perpendicular to each other, and can be driven without unnecessary distortion such as rotation and twist for reducing optical signal errors.
In this conventional optical actuator, since the objective lens secured in a lens holder is driven up and down, and left and right directions for focusing and tracking operation, a driving device utilizes the Lorentz Force by Fleming""s left-hand rule using a coil arranged in a magnetic field formed by a magnetic and a magnetic substance.
FIGS. 1A and 1B schematically shows a conventional optical pick-up actuator. As shown in FIGS. 1A and 1B, the conventional optical pick-up actuator includes a lens holder 102 securing an objective lens 101, a magnet 103, a yoke 104, a tracking coil 105, a focusing coil 106, a plurality of wire springs 107, a fixed print circuit board (PCB) 108, and a frame 109.
The objective lens 101 is seated at a center of the lens holder 102 and the lens holder 102 is movably arranged with a plurality of wire springs 107. The lens holder 102 secures the objective lens 101 at the center thereof and is wound by the focusing coil 106, and then a previously wound tracking coils 105 are mount around the lens holder 102 over focusing coil 106. Next, the PCBs 108 is fixed on both sides of the lens holder 102 and a pair of yokes 104 are arranged so as to face each other. On an outer surface of each yoke 104, a magnet 104 is fixed.
Also, the yoke 104 is integrally formed with a pick-up base and (not shown) through a hole by an integral member.
On one side of the optical pick-up actuator, a frame 109 is arranged such that a main PCB is fixed thereto using a bolt (not shown), and a plurality of wire springs are connected to the main frame 109. The wire springs 107 are connected to the fixed PCB 108 such that the lens holder 102 is suspended by the wire springs 107.
In the above structured optical pick-up actuator, if an electric current flows along the focusing coil 106, an electromotive force is generated such that the electromotive force can drive the movable part (lens holder assembly) in upward and downward directions. Identically, if the electric current flows along the tracking coil 105, an electromotive force is generated such that the electromotive force can drive the movable part in left and right directions (tracking directions).
By tracking and focusing controls of the optical pick-up actuator, the pick-up actuator maintains focusing depth of the laser beam projected from the objective lens 101 so as to read information pits on the optical disc and moves along the tracks formed on the optical disc.
However, this conventional pick-up mechanism is inappropriate for controlling the recording/reproducing operation if the data storing volume of the disc increases. The increase of storing volume means that the data recorded along each track increases such that the number of the tracks of the optical disc increase.
That is, in conventional low density optical disc, it is possible to successively read or write information signals by controlling movement of the optical pick-up and optical lens of the actuator. In the high density optical disc; however, the track width is narrow such that the conventional control method can not be used for tracking and focusing the disc.
The present invention has been made in an effort to solve the above problems of the prior art.
It is an object of the present invention to provide an optical actuator capable of controlling tilt necessary for read information signals from a high density optical disc and write the information signals on the disc.
To achieve the above object, the optical pick-up actuator of the present invention comprises a lens holder surrounding an objective lens, a pair of tracking coils, and a pair of focusing coils; a frame for suspending the lens holder in a magnetic field using suspension wires; and a pair of tilt driving magnetic circuit for driving the actuator in a third direction but not focusing and tracking directions. The optical pick-up actuator can tilt the frame in a magnetic field by the tilt driving magnetic circuit so as to tilt the lens holder connected to the frame via the suspension wire.